The present invention relates to high performance, compact electro-acoustic transducers. More specifically, the invention relates to non-woven composite spiders used in these compact electro-acoustic transducers.
A spider and surround provide a suspension system for a diaphragm in an electro-acoustic transducer. Both the spider and surround support the diaphragm as it moves along the transducer axis and prevents a voice coil attached to the diaphragm from rubbing against or hitting the transducer's pole piece or pole plate. The spider and surround are typically ring-shaped having an inner and outer perimeter. The outer perimeters of the spider and surround are attached to the transducer's basket. The inner perimeter of the surround is typically attached to the outer edge of the diaphragm. The inner perimeter of the spider is typically attached near a narrow portion of the diaphragm or to a bobbin.
Spiders are typically made by dipping a woven fiber such as cotton in a phenolic resin. The woven cotton provides strength and fracture toughness to the spider and the phenolic resin provides enough stiffness to maintain the spider's shape while providing enough compliance to allow the diaphragm to freely move along the transducer axis. The phenolic resin coats the fibers and forms bridges between the warp and weft yarns where the yarns overlap. The resin bridges provide stiffness to the coated fiber while allowing air to pass through interstices between the woven fabric. The phenolic-resin-fiber-coated spider is herein referred to as the typical spider.
As the diaphragm moves in and out along the transducer axis, the spider is repeatedly flexed or stretched to accommodate the movement of the diaphragm. The repeated flexing/stretching of the spider typically leads to a fatigue-type failure, thereby shortening the life of the electro-acoustic transducer. Furthermore, the flexing/stretching of the spider generally reduces the stiffness of the spider over time (ageing), which may affect the acoustic properties of the electro-acoustic transducer.
Consumer pressure favors the design of high-power, compact electro-acoustic transducers, which usually requires longer stroke distances for the diaphragm. The longer stroke distance generates larger cyclic stresses in the spider and accelerates the ageing of the spider and shortens the live of the spider. Therefore, there remains a need for compact spiders that can support the longer stroke distances of the diaphragm with increased fatigue and ageing resistance.